The Independent Commission Against Corruption's (ICAC) counsel assisting, Geoffrey Watson SC, has apologised for his conduct during a tense exchange with former New South Wales energy minister Chris Hartcher.

Mr Watson repeatedly locked horns with Mr Hartcher on Monday as Mr Hartcher was grilled about his involvement with the alleged Liberal Party slush fund, Eightbyfive.

Mr Hartcher was also accused of laundering $4,000 through the trust account of his old law firm, Hartcher Reid.

At times the exchange between the pair descended into a shouting match, and ICAC commissioner Megan Latham had to tell both men to "take a backwards step" and stop "acting like squabbling children".

Mr Watson began this morning's proceedings by promising not to let it happen again.

"I could try to blame it on the fact that I'm tired, or the fact that I'm red-haired."

He added that regardless of the cause, he would try to improve his behaviour.

Ms Latham also warned all the barristers in the room that a lot of "irrelevant and unhelpful" asides were being picked up by the microphones in the room.

She said they had so far been omitted from ICAC transcripts, but if they continued, she warned, she would order them to be included, and it would be "embarrassing" for those who made the comments.

ICAC evidence 'not good publicity' for Liberals

Mr Hartcher was far more subdued during cross-examination today than during his verbal clashes with Mr Watson yesterday.

He remained adamant that he was not involved in any corrupt schemes.

Mr Watson has described Mr Hartcher as the mastermind of alleged Liberal party slush fund Eightbyfive and accused him of soliciting payments in return for political favours.

But Mr Hartcher used his final minutes in the witness box to reject an idea that had been raised about him at the previous ICAC inquiry - that he may have been the person who had told a journalist about Liberal Party fundraiser Nick Di Girolamo's now infamous gift of a bottle of wine to former premier Barry O'Farrell.

He said he deeply resented such a "reckless" question being asked by the counsel assisting at the previous inquiry, and conceded that may have contributed to his attdtude towards Mr Watson yesterday.

Mr Hartcher denied that the founder of alleged slush fund Eightbyfive, Tim Koelma, was doing paid work in his office when he was also doing contract work with Australian Water Holdings (AWH), saying he was just a Liberal Party volunteer.

He has been grilled about whether he pushed Mr Koelma to insert a confidentiality clause in the contract with AWH because he knew it would be a "bad look" for someone in his office to also be on AWH's payroll.

Mr Hartcher rejected that but added that it was now "pretty self evident that this is not good publicity for me or the Liberal Party".

He denied any knowledge of a false corruption complaint Mr Koelma has been accused of making against a senior public servant who stood in the way of AWH's plans.

Mr Hartcher left the building's underground carpark in a car pursued by photographers.

ICAC's public hearings into the current inquiry have now been adjourned until August.